Ultrasound

What is ultrasound?

Ultraschall

Ultrasound refers to a frequency spectrum of sound beyond the audible range for humans, starting from about 16 kHz (kilohertz) to 1.6 GHz(gigahertz). Ultrasound waves always require a medium through which to propagate. This could be air, water or any other solid or liquid. Basically, ultrasound propagates as a so-called longitudinal wave.

Air-borne noise can only transition into a solid body if the sound wave is emitted within immediate proximity, and if there is a coupling medium of a specific density and appropriate acoustic properties in between. Depending on the properties of an obstacle, ultrasound will either be reflected from it, absorbed by it or simply transmitted through it. As with all wave types, diffraction, refraction and interference can all occur with ultrasound. Basically, ultrasound transmits very readily through a closed, humid environment. The penetration depth of ultrasound depends primarily on the frequency used and the amplitude (or strength) of the signal. The rule with ultrasound is: the lower the frequency, the deeper the sound wave penetrates into the tissue. This is rather ironic, in an age where the market typically wants everything to go "faster, higher and further". For medical and cosmetic treatment, there are two different ways to employ ultrasound:

  1. Continuous ultrasound: In this case, the sound is produced continuously and output at a specific frequency and amplitude (strength) of the signal.
  2. Impulse ultrasound: This is where a specific frequency and amplitude is output in discrete pulses.

An advantage of continuous ultrasound over impulse ultrasound is that it always involves a heating reaction. Care must be taken when working with veryhigh amplitudes, however – if the ultrasound remains too long on one point oftissue, then it can lead to a so-called "hotspot" (strong warming to the point of excessive heat).

 

Applications of ultrasound in medicine and cosmetics

Diagnostics:
This field is probably the most well known and most widely used application of ultrasound. In 1942, neurologist K.-T. Dussik from Vienna, Austria used his "hyperhponography" method to produce the first transmission ultrasound image, or "hyperphonogram", of a human skull (published in the Journal of Neurological Psychiatry 1942). Originally viewed with skepticism, this diagnostic method gained widespread acceptance by the end of the 1950s. The pioneer in the development and production of systems for medical use was, and still is, the Siemens Group of Germany. These days, given greater computational power and optimized scanning methods, we can already produce three or four-dimensional pictures for better differential diagnostics using ultrasound technology (spatial compounding and frequency compounding). Ultrasound diagnostics is considered a highly-developed, reliable, gentle and safe diagnostic method, and we can no longer imagine classical medicine without it.

 

Therapy:
The therapeutic use of ultrasound is essentially based on three different principles of action:
The thermal action – the kinetic energy of the sound inside the tissue is converted into heat when employing ultrasound (molecular collusion). Continuous ultrasound waves are used to produce this effect. With the mechanical action, the sound waves cause vibration in the tissue, which leads to a so-called micro-massage. In physical medicine, pulsed sound waves are used here as well, where no heating effect occurs. The third action is sonophoresis (also known as phonophoresis). This is where the properties of ultrasound are used for transcutaneous (penetrating beneath the skin) transport of active ingredients. Ultrasound optimizes the permeability of tissue structures, thereby transporting active ingredients to deeper regions of the organism than they would otherwise reach by other methods. In dentistry, ultrasound has been used for a very long time as a gentle means of cleaning teeth. Other applications in medicine include eye surgery, separation and fusion of tissue and bone, tumor therapy, tissue cleaning, germ killing and biostimulation at the cellular level. Very recently, in 2009, the first non-invasive brain operation using transcranial high-energy ultrasound technology was performed in Switzerland (Universitätsspital Zurich), under observation with magnetic resonance imaging.

Cosmetics
:

The first cosmetic uses of ultrasound followed after some interesting results were obtained in physical medicine. Patients were surprised when they saw that the skin in the areas that were treated with ultrasound (e.g. for muscle relaxation) had visibly improved. The skin was tighter and more elastic, and impurities had disappeared. When one considers the fundamental action of ultrasound frequencies, however, these observations make absolute sense. Subsequently, people started experimenting with various frequencies within the ultrasound spectrum and different specific doses. The first ultrasound device for cosmetic use was presented in Germany in 1989. At the time, it still took a lot of convincing to establish this previously unheard of method in cosmetic institutes. Nowadays, there are two different frequency systems used, 1 MHz and 3 MHz. 3 MHz systems only reach the epidermis (outer layer), while 1 MHz systems reach all layers of the skin, down to the connective tissue, and are still regarded as "state-of-the-art". Following countless trials and research studies, the optimal intensity of sound (measured in Watts per square centimeter, W/cm²) that is still safe has been calculated at 0.5–1 W/cm². Once the perfect combination of controlled penetration depth, optimal intensity and simple and safe use with no side-effects was found, home-use cosmetic ultrasound treatment was born. It was now possible to produce compact devices for daily home use. In 2003, MediConsult developed the first "SkinDream", which immediately met with wide acceptance in cosmetics businesses and, above all, in homes. The SkinDream® TITANIUM was presented to the world in 2009. The first, and so far only, cosmetic ultrasound system for home use that features its own hand-made titanium sonic head.

 

Effective actions of cosmetic ultrasound on and in the skin.

Thermal action

Heating the skin tissue leads to improved blood circulation, and thereby an immediate increase in metabolic activities, accelerating cell regeneration.

Mechanical action

The frequency of the ultrasound employed stimulates the tissue into faster oscillations around its resting position. This leads to periodical compression and decompression in the tissue mass. At an optimal dosage (0.5–1 W/cm²) and at the right frequency (1 MHz), a so-called micro-massage effect begins to work on the applied tissue. This immediately promotes the detoxification process and lymph drainage within the skin layers, and accelerates the diffusion process in the tissue.

Combination of thermal and mechanical action

Given the combination of these two actions, the pH of the skin starts to shift towards a more alkaline level. This leads to a stimulation of collagen and elastin, improving resilience and revitalizing the skin.

Sonophoresis

This term describes the phenomenon of cosmetic ultrasound transporting micro-ingredients into the layers of the skin. Unlike iontophoresis (channeling drugs and medicines with the help of electrical currents/ionization), ultrasound does not directly push the micro-ingredients into the skin. The micro-massage merely induces a "door opening" and a cleaning of the interstitial spaces between cells in the skin, thereby improving the skin's permeability. Drugs then penetrate through these and into the deeper skin layers as a result of the normal metabolic processes. Biomolecules and non-ionized active ingredients can only be effectively transported into the skin using cosmetic ultrasound. Laser systems and devices based on the principle of iontophoresis (galvanic systems) are not able to guarantee this extremely important function for effective, lasting skin regeneration.

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